There appears to be a trend to have put the brake on an increase in the number of smokers through the years. However, the disease rate of lung cancer and the death toll due to the lung cancer are still maintained at high numerical values. For instance, the medical institution of US estimates that the rate of incidence of the lung cancer will increase.
This is considered to occur due to, for example, the problem of asbestos or the like and such environmental factors as to increase the rate of lung cancer incidence.
There has been an extremely strong demand for early detection of diseases, particularly, lung cancer under such conditions. Various techniques have been developed even in relation to the diagnosis of lung cancer.
If part of lung tissue is detected from within the body of a subject and the lung tissue is analyzed pathologically, it is then possible to determine the presence or absence of affection with lung cancer with high accuracy. It is however necessary to make an incision in body surface portion of the subject for the purpose of taking out the tissue to be analyzed from within the body of the subject. This puts an enormous load on the subject.
Therefore, there has been a demand for determination of the presence or absence of a disease, particularly, lung cancer without making an incision in the tissue of the body of the subject as much as possible, in other words, by an non-incision method.
To meet such a demand, there has been provided, for example, a technique for administering fluorescent target-oriented structure having biocompatibility specifically taken in due to tumor tissues to a subject, projecting excitation light having wavelengths ranging from 401 nm to about 500 nm onto the subject and observing fluorescence emitted by irradiation of the target-oriented structure to thereby determine the presence or absence of cancer tissues (refer to a patent document 1).
According to the above prior art, however, there is a need to administer the fluorescent target-oriented structure to the subject. There exists the subject that feels extreme anguish against such administration.
As a method for diagnosing lung cancer by a non-incision method other than the above, there exists a technique for analyzing and determining various body fluids, secretions or excrements as an alternative to the detection of the body tissues by the incision of the body surface portion. Upon handling of the body fluids, secretions or excrements, however, a large amount of labor is required to achieve the diffusion into an ambient environment. Further, there also exists a case in which each subject feels emotional distress and physical pain against the submission of such body fluids, secretions or excrements to doctors or the like corresponding to others.
Although various ones have been proposed as methods for diagnosing diseases, particularly, lung cancer even in addition to above, they present problems in terms of the accuracy of diagnosis.    Patent document 1: Japanese Patent Laid-Open No. 2004-527299